How can I fix my Hotpoint Aquarius CTD00 Tumble Dryer?

Hi There, I Dont know if its possible to fix myself, But Im willing to give it a go!...My Dryer makes avery loud racket while in use as if there is a metal object inside!..when I turn it off, it also makes a loud noise (sounds so loud as if its going t blow up!) Iv had the Dryer for about 3 years now and had a repair within first three months of Timer Thermostat relay (If I remember correctly) it was getting stuck so repair man fitted new Thermostat. Any Ideas what could be the problem please? Many Thanks.